The invention relates to an electronic flash, and more particularly, to an electronic flash having a number of illumination modes including automatic and manual control modes.
An electronic flash for use with a camera is known which is capable of producing illumination in a number of control modes including TTL (through the lens) automatic mode, usual forms of automatic illumination control modes and manual mode. Specifically, a TTL automatic illumination control mode employs direct photometry of TTL type in which an electronic flash is mounted on a single lens reflex camera including an electrical shutter so that reflective light from an object being photographed, which is illuminated by radiation from the electronic flash, is subject to photometry within the camera to produce a signal when proper exposure is reached to interrupt the illumination in an automatic manner, while simultaneously closing the shutter of the camera. In short, this mode provides an automatic control of illumination from the electronic flash by utilizing photometric means which is provided as part of the camera. The usual form of automatic illumination control modes utilize a photometric device which is provided as part of the electronic flash. This photometric device determines reflective light from an object being photographed to interrupt the illumination from the electronic flash whenever a proper exposure is reached while simultaneously causing the shutter of the camera to be closed. A manual illumination control mode which is widely used establishes a diaphragm of the camera in accordance with a guide number and a distance to an object being photographed to control the electronic flash. Certain electronic flashes are also available in which modified guide numbers can be used during the manual mode.
When an electronic flash having the capability to be operated in any of these illumination modes is used, a desired mode can be selected depending on the type of camera on which it is mounted or as the user desires, by a switching means provided on the electronic flash in the form of a rotary or sliding switch. As the switch is operated, an indicator table provided on the back of the electronic flash which gives a list of diaphragm values against distances to an object being photographed as well as a film speed indicator table are modified in accordance with the switch setting. Such indicator tables are only necessary during the manual mode, but are unnecessary when the TTL or a usual automatic control mode is chosen. When these modes are chosen, proper exposure is automatically assured without the use of such indicator tables. Nevertheless, if these indicator tables remain exposed, a user may think they should be used. Hence, it is desirable that such indicator tables be capable if being hidden from the view of the user during operation in the automatic modes.
Conversely during the manual illumination control mode, the diaphragm value and film speed indicator tables are shifted in accordance with a different set of guide numbers, so that it is also desirable that indications other than those associated with a selected guide number be hidden.